conf/112997: [patch] Add note about the 'native' mtune option to share/examples/etc/make.conf

[b. f.]

The following reply was made to PR conf/112997; it has been noted by GNATS.

From: "b. f." <bf1783 at googlemail.com>
To: bug-followup at FreeBSD.org
Cc: Scot Hetzel <swhetzel at gmail.com>
Subject: Re: conf/112997: [patch] Add note about the 'native' mtune option to share/examples/etc/make.conf
Date: Sun, 5 Sep 2010 01:22:03 +0000

 It is very inefficient to invoke gcc, grep, and/or awk every time this
 makefile is processed.  (In the past, we've gone to a great deal of
 trouble to avoid this kind of thing:
 
 http://lists.freebsd.org/pipermail/freebsd-ports/2008-July/049777.html
 http://lists.freebsd.org/pipermail/cvs-ports/2008-July/153224.html
 
 )  Instead, I think that comments in /etc/make.conf instructing users
 to how to correctly specify their CPUTYPE would be appropriate.  The
 list of overrides for the base system compiler should be expanded, and
 perhaps relaxed if CC != cc.  But _all_ overrides cannot be removed,
 and MACHINE_CPU cannot be expanded to include all features recognized
 by compilers from ports, because the kernel lacks the necessary
 support for things like SSE5/XOP+FMA4+CVT16, LWP, AVX, etc.
 
 b.